Manufacture of open-hearth steel.



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HERBERT c. mmme AND ANSON w. ALLEN, or BIRMINGHAM, ALABAMA.

MANUFACTURE OF OPEN-HEARTH STEEL.

IEO Drawing.

metal for the charge, whereas previously a substantialquantity of steel scrap has generally been charged with the lime and iron oxid before the addition of the blown metal to the furnace. This process of using all blown metal Works very economically and rapidly and produces a fine quality of steel.

The charge is made up of blown metal and slag-forming materials, usually lime, iron oxid and manganese ore. The blown metal is taken from the converter in any number of successive ladles. First, there are taken several ladles of metal blown low in carbon and finally a ladle, or ladles, of metal blown high in carbon. F or example, when five ladles constitute this full charge, the first four ladles may be blown down to about 0.06 per cent. carbon and the fifth ladle of metal blown only down to about 2.50 to 3.00 per cent. carbon. The charge of blown metal is thus secured of a desired intermediate carbon percentage whichis difficult to secure with the same exactness in the Bessemer operatlons. The Bessemer operation is so fast that it is diflicult to stop it at a Bessemer operations are made easy and the.

successive ladles for the open hearth can be produced exactly as required.

Where the slag-formmg materials are introduced first and the blown metal afterever, that this difficulty can be corrected by reversing the order of introduction of the blown metal and the slag-forming materials. We, therefore, use'two alternating opera- Specification of Letters Patent. Patented 24, 1918..

Applicationfiled July 6, 1917. Serial No. 178,930.

' tions,tone serving to build up the bottom and the other to erode it.

We alternate these operations as required and thus maintain a bottom which is sufliciently uniform for all practical purposes. It is not necessary to shift from one operation to the other ,for each successive bath ofmetal. We may use one operation until the bottom is too far built up or too far eroded and then use the other until the opposite condition is obtained, and so on. A specific example is as follows:

Aftercompleting repairs to the bottom of the furnace which are usual before charging, we introduce the necessary quantity of lime on the bottom and the necessary quantity of iron oxid and-manganese ore on top of the lime. We introduce immediately after the introduction of the slag materials referred to four ladles of converter metal averaging about 45,000 pounds each, this metal being of soft steel quality, having the silicon and manganese blown out and the carbon reduced to about 0.06 per cent. The bath is then heated for one and a half to two hours, until the bath and slag are in I proper condition. A fifth ladle of high carbon blown metal is then added, the carbon being from 2.50 to 3.00 per cent.

The carbon in the last ladle combines very rapidly with the oxygen in the bath and in the slag and sets up a violent agitation, durin which the phosphorus in the metal is rapidly oxidized and passes from the bath into the slag; the purification of the metal being facilitated by the heating effect of the oxidation of the phosphorus and of the combustion of the gas in the furnace.

These reactions are allowed to continue until the bath is brought to the desired composition and' temperature for tapping or pouring. Before tapping we have found it advisable to add about 1,000 pounds of cold pig iron for the purpose of correcting any over oxidized condition of the bath and to secure a desired carbon content therein. The time required to add the last ladle of metal from the converter and to finish the heat ready'for tapping is about two or two and a half hours.

In tapping we may add coke dust for recarburization and ferro-manganese and of the specification. The furnaceis completely' .drained of both steel and slag, completing the cycle of one operation, and referro-ilicon according to the requirementspairs are then made to the banks and bottombf the furnace asfaras may be necessary before the next heat.

,. After these repairs'are made, and suppesing the'above operations have been 're- .peated to such an extent that the bullding up 'of the bottom has become ob ect1onable,

I we first charge four ladles of converter then adding high carbon molten blown metal andfinishing the operation and pouring the ,charge; so that the first operation will serve to build upthebottom of the furnace and metal of 0.06 per cent. carbon averaging \hearthsteel from all I blown metal, the about 45,000 pounds each. After c'o'mpletmethod which comprises the following two ing this lnetal charge of four ladles we add alternat ng operations: (1) charging the the necessary quantity of lime and then iron open hearth furnace first with lime and iron oxid.- We then heat the bath until we find oxid and then with about four parts. of

the slag in proper condition, usually one molten converter metal blown-down to about and a half to two hours, and then add a 0.06 per cent. carbon, heating until the bath fifth ladle of,high carbon blown metal, the and the slag are in proper condition and carbon about 2.50 to &00 per cent. The thenadding aboutone part of molten confinishingsteps(arethen car'ried out as de- 'verter metal blown to about. 2.50: to 3.00 scribed in connection with the first op'era per cent. carbon and finishing the operation tion. By this method "of charging we-have. and pouring the charge; and (2) charging discovered that the bottom instead of buildthe open hearth furnace first with about ing up is slightly eroded; so much so, in four parts of molten converter metal blown' fact, that we are'enabled' bycharging the to. about 0.06 per cent. carbon and then I furnace one way or. the other, depending with lime and ironoxid, heating until the adding blown metal. [And the term slag upon the'condition of the bottom,'to'mainbath and slag are in proper condition'and tain a practically uniform bottom. 7 then adding about one part of molten con- In the above example we have described 'verter metal blown to about 2.50 to 3.007 per the adding of theslag materials in solid cent. carb0n and finishing the operation and condition and the adding of the metal while pouring the charge; so that the first operathe slag materials are still solid. We may, tion will serve to build up the bottom-of however, melt the slag before introducing the furnace and the second to erode it and it; or after introducing it into the open the alternating operations will maintain'it hearth furnace we may melt it there before approximately uniform.

3. In the manufacture of basic open is used herein to cover either the solid ma hearth steel from all' blown metal, the tei-ials or the molten slag. This application method which comprises charging the open is intended to include both methods; a sephearth furnace first with lime and iron oxid arate divisional application (No. 178,931) being filed herewith to coverspecifically the carbon, heating until the bath and the slag adding of the metal to moltenslag. 'Variare in proper condition and then adding ous other modifications may be made in the high carbon molten blown metal and finishmethod which comprises the following two several steps of the process and in the order ing the operation. of such steps and the specific compositions of the charge by those skilled in the art hearth steel from all blown metal, the without departing i from the invention as method which comprises charging the open defined in'the following claims. And either hearth furnace first with lime and iron oxid of the operations above described may be and then with about four parts of molten alternated with some'building-up or eroding converter metal blown to about 0.06- per operation (as the case may require) other cent-carbon, heating until the bath and the than that herein described. a slag are in proper condition and then add- What we claimis: ,ing about one part of molten converter metal 1. In the manufacture of basic open: hearth steel fromallblown 'metal, the and finishing the operation.

5. In the manufacture of basic open alternating operations: (1) charging the hearth .steel from all blown metal, the

-'furnace first with lime and iron oxidand method which comprises charging the open then with low carbon molten blown metal, hearth furnade first-with low carbon molten heating until the bath and the slag are in blown metal and then with lime and iron proper condition and then adding high car oxid, heating until the bath and slag are bon molten blown metal and. finishing the in proper condition'and then adding high operation and ouring the charge; and .(2) carbon molten blown metal charging the 05911 hearth furnacefirst with operation. I low carbon molten blown metal and then '6. In the manufacture of basic open with lime and iron oxid, heating until the hearth steel from all blown metal, the

4. In the manufacture of basic open and finishing the and then with molten blown metal low in blownto about 2.50 to 3.00 per cent. carbon '65 bath and slag are in' proper condition and method which comprises charging the open hearth furnace first with about four parts two operations, one serving to build up the of molten converter metal blown to about bottom of the furnace and the other to erode 0.06 per cent. carbon and then with slag, it, alternating these operations asrequired heating until the bath and slag are in to maintain an approximately uniform 5 proper condition and thenadding about one bottom. 15 part of molten converter metal blown to In witness whereof, we have hereunto about 2.50 to 3.00 per cent. carbon and finsigned our names. ishing the operation. l

7. In the manufacture of, basic open HERBERT C. RYDING. 10 hearth steel, the method which comprises ANSON W. ALLEN. 

